This invention relates to the recording head of an ink-jet printer which uses a fluoroplastic orifice plate or an orifice plate having a fluoroplastic layer formed on the surface of a base, characterized in that the surface of either type of orifice plate is treated to become super-water-repellent, or treated to become more water-repellent than the water-repellent fluoroplastic bulk material. The invention also relates to a process for producing the recording head.
A typical process for producing the recording head of a thermal ink-jet printer comprises the steps of preparing a semiconductor device (the main body of the head) by forming a drive circuit and heaters (thin-film resistors) on a silicon substrate, opening ink supply holes through the silicon substrate from the back side and forming a cavity on each heater that serves as an ink chamber, attaching an orifice plate to the entire surface of the semiconductor device (the main body of the head), and opening each ink ejection orifice (nozzle) in a position corresponding to each heater.
It is known that the areas around the orifices in the recording head of an ink-jet printer (hereunder sometimes referred to as an ink-jet recording head) can generally be provided with consistent ink ejection characteristics by imparting water repellency. Therefore, in order to impart water repellency to the surface of the orifice plate, it has heretofore been attempted to coat the surface of the orifice plate with a fluoroplastic film, or implant ion molecules containing fluorine atoms into the surface of the orifice plate, or form tiny asperities on the surface of the orifice plate.
For instance, JP 6-316079 A discloses an ink-jet recording head in which the very limited areas peripheral to the ink ejection ports are coated with C2F4+ ions by the method of inorganic Ion implantation to be rendered water-repellent. JP 10-151744 A discloses an ink-jet recording head in which tiny asperities with sizes of 10-100 nm are formed on the surface of an orifice plate such that not only its surface but also the inner surfaces of the orifices within a depth of 3 xcexcm from the surface become water-repellent.
Therefore, from the viewpoint of water repellency, it is preferred to use a fluoroplastic orifice plate or an orifice plate having a fluoroplastic layer formed on the surface of a base. However, fluoroplastics inherently have high level of water repellency and very poor adhesion, so it has been extremely difficult to attach the orifice plate to the semiconductor device or form mask materials such as photoresist and metal mask on the orifice plate before opening (boring) orifices.
The present invention has been accomplished under these circumstances and has an object providing a recording head which uses a fluoroplastic orifice plate or an orifice plate having a fluoroplastic layer on the surface and which is characterized in that the surface of either type of orifice plate is treated to become super-water-repellent.
Another object of the invention is to provide a process for producing the recording head.
In order to attain the object described above, the first aspect of the present invention can also be described as a recording head of an ink-jet printer which comprises a main body having ink ejection devices and a device for driving the ink ejection devices independently, and an orifice plate the other side of which is attached to the main body and which has ink ejection orifices opened in the positions corresponding to the ink ejection devices, the orifice plate having at least one side formed of a fluoroplastic, the surface of the one fluoroplastic side having been treated to become more water-repellent than the bulk material of the fluoroplastic whereas the surface of the other side of the orifice plate is more hydrophilic than the bulk material of the fluoroplastic, and said more water-repellent surface of the one fluoroplastic side containing more fluorine atoms than are inherently present in the fluoroplastic in an untreated state.
Preferably, the orifice plate is composed of a fluoroplastic member and is such that the surface of the other side which is attached to the main body has been treated to become more hydrophilic than the bulk material in an interior of the fluoroplastic member whereas the surface of the one side has been treated to become more water-repellent than the bulk material and the more water-repellent surface layer of the fluoroplastic member contains more fluorine atoms than are inherently present in the bulk material in the interior of the fluoroplastic member in the untreated state.
Preferably, the orifice plate comprises a base which is more hydrophilic than the bulk material of the fluoroplastic itself at the other side of the orifice plate and a fluoroplastic layer formed on the base at the one side, a surface of the fluoroplastic layer having been treated to become more water-repellent than an interior of the fluoroplastic layer, and the surface of the fluoroplastic layer treated to become more water-repellent contains more fluorine atoms than are inherently present in the interior of the fluoroplastic layer in the untreated state.
In order to attain another object described above, the second aspect of the present invention can also be described as a process for producing a recording head of an ink-jet printer comprising the steps of preparing an orifice plate having at least one side formed of fluoroplastic, treating the surface of the one fluoroplastic side to become more hydrophilic than the bulk material of the fluoroplastic, attaching the other side of the orifice plate to the main body of a head having ink ejection devices and a device for driving the ink ejection devices, the other side being more hydrophilic than the bulk material of the fluoroplastic, forming on the one side of the orifice plate a mask for masking the regions of the orifice plate other than those corresponding to the ink ejection devices, using the mask to open ink ejection orifices in the orifice plate at the positions corresponding to the ink ejection devices, removing the mask, and implanting ions into the surface of the one fluoroplastic side of the orifice plate so that the surface is treated to become more water-repellent than the bulk material of the fluoroplastic.
Preferably, the orifice plate itself is made of the fluoroplatic, and the treating step to become more hydrophilic is a step of treating both sides of the orifice plate made of the fluoroplastic to become sore hydrophilic than the bulk material of the fluoroplastic.
Preferably, the orifice plate comprises a base which is more hydrophilic than the bulk material of the fluoroplastic itself at the other side of the orifice plate and a fluoroplastic layer formed on the base at the one side of the orifice plate, the treating step to become more hydrophilic is a step of treating a surface of the fluoroplastic layer formed at the one side of the orifice plate to become hydrophilic, the mask is formed on the fluoroplastic layer of the orifice plate, and the implanting step is a step of implanting ions into the surface of the fluoroplastic layer of the orifice plate so that the surface is treated to become more water-repellent than the interior of the fluoroplastic layer.
Preferably, the fluoroplastic layer is formed by applying a fluoroplastic coat to the base, vapor-phase deposition of a fluoroplastic film on the base, or bonding a fluoroplastic sheet to the base.
Preferably, the ions are implanted only into regions of a specified range including those where the ink ejection orifices are opened, with the other regions being masked by the mask.